Broadly, how can we categorise materials?

It seems like there is a lot of materials out there. Just look around where you are right now and I am sure there are many materials. Just looking around me there is wood in my desk, plastic in my bottle, metal in my watch, paper in my books etc. I’m sure you can conduct the same exercise.

We can group most materials into either metals, ceramics or polymers/plastics. These broadly share the same properties.

Metals. These are quite recognisable to people as they are typically shiny, hard and generally metallic. Characteristics include high thermal/electrical conductivity. They are malleable and have a high mechanical strength. The reason for these characteristics are the ‘sea of non localised electrons’ around the lattice of positive ions. Metals are normally expensive as they must be sourced from other compounds. A common example of this is iron ore (magnetite/hematite), which needs to be heated to a high temperature to reveal the iron within. Due to the fact metals make compounds easily they are vulnerable to corrosion

Polymers. ‘Poly’ means many and a polymer is many molecules linked together in things known as hydrocarbon chains(hydrogen and carbon bonds repeating) For example polystyrene is a repeating chain of the monomer styrene. Polymers are low density and unstable at high temperatures but can easily be shaped. Very unreactive and solid at room temperature. Low cost and ability to shape means they have LOTS of uses, water bottles for example. An issue is that bottles will not degrade easily as the polymers comprising the plastic is unreactive.

Ceramics. Due to covalent bonding (many oxides, carbides, nitrites) in many ceramics there are little free electrons and therefore they are not very conductive thermally or electrically. Stiff as there are few dislocations that can pass through the material. High strength too (strong under compression) and resistant to corrosion/high temperature. Bricks, plates and bathroom tiles are common ceramics you come across in day to day life. They are made by moulding a ceramic powder with water that will be heated to remove the water and oxidise the powder. Hence going into a kiln.

There are other materials like composites but these are simply combinations of these primary three.

Thanks to this website and this website

More about iron ore


Please tell me if I have got anything wrong or if you would like to add anything


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